linux-kernel - Re: [RFC PATCH] edac: add support for ARM PL310 L2 cache parity

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Message-ID: <CAL_Jsq+gszc+R_BrLtHKEBGYd=3T+sE1d+-HoF9aYZt6C2k5-g@mail.gmail.com>
Date:	Wed, 9 Apr 2014 08:18:28 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>,
	Doug Thompson <dougthompson@...ssion.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-edac@...r.kernel.org, Michal Simek <michal.simek@...inx.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Rob Landley <rob@...dley.net>, kpc528@...il.com,
	kalluripunnaiahchoudary@...il.com, punnaia@...inx.com
Subject: Re: [RFC PATCH] edac: add support for ARM PL310 L2 cache parity

On Wed, Apr 9, 2014 at 6:32 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Sun, Mar 02, 2014 at 08:02:40PM +0530, Punnaiah Choudary Kalluri wrote:
>> Add support for ARM Pl310 L2 cache controller parity error
>>
>> Signed-off-by: Punnaiah Choudary Kalluri <punnaia@...inx.com>
>> ---
>>  .../devicetree/bindings/edac/pl310_edac_l2.txt     |   19 ++
>>  drivers/edac/Kconfig                               |    7 +
>>  drivers/edac/Makefile                              |    1 +
>>  drivers/edac/pl310_edac_l2.c                       |  236 ++++++++++++++++++++
>>  4 files changed, 263 insertions(+), 0 deletions(-)
>>  create mode 100644 Documentation/devicetree/bindings/edac/pl310_edac_l2.txt
>>  create mode 100644 drivers/edac/pl310_edac_l2.c
>>
>> diff --git a/Documentation/devicetree/bindings/edac/pl310_edac_l2.txt b/Documentation/devicetree/bindings/edac/pl310_edac_l2.txt
>> new file mode 100644
>> index 0000000..94fbb8d
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/edac/pl310_edac_l2.txt
>> @@ -0,0 +1,19 @@
>> +Pl310 L2 Cache EDAC driver, it does reports the data and tag ram parity errors.
>> +
>> +Required properties:
>> +- compatible: Should be "arm,pl310-cache".
>> +- intterupts: Interrupt number to the cpu.
>> +- reg: Physical base address and size of cache controller's memory mapped
>> +  registers
>> +
>> +Example:
>> +++++++++
>> +
>> +     L2: cache-controller {
>> +             compatible = "arm,pl310-cache";
>> +             interrupts = <0 2 4>;
>> +             reg = <0xf8f02000 0x1000>;
>> +     };
>> +
>> +PL310 L2 Cache EDAC driver detects the Parity enable state by reading the
>> +appropriate control register.
>> diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
>> index 878f090..059ac31 100644
>> --- a/drivers/edac/Kconfig
>> +++ b/drivers/edac/Kconfig
>> @@ -326,6 +326,13 @@ config EDAC_TILE
>>         Support for error detection and correction on the
>>         Tilera memory controller.
>>
>> +config EDAC_PL310_L2
>> +     tristate "Pl310 L2 Cache Controller"
>> +     depends on EDAC_MM_EDAC && ARM
>> +     help
>> +       Support for parity error detection on L2 cache controller
>> +       data and tag ram memory
>> +
>
>
> Ok, so I'm looking at this after having looked at the synopsys thing
> and it looks very similar in functionality - it does the basic dance of
> registering and setting up stuff, only using different devicetree nodes,
> regs, etc.
>
> However, it adds a new file under drivers/edac/ and I'm wondering if it
> wouldn't be better to simply create a xilinx_edac.c and put all your
> stuff in there, maybe even share code by abstracting it nicely. Having
> a separate driver only for a single L2 cache controller seems kinda too
> granulary for me.

I don't think so, the PL310 is present on lots of ARM chips besides
Xilinx. I don't know how many support parity as that is optional. In
fact the highbank_l2_edac.c is for the PL310 as well, but the
registers it uses is all custom logic added for ECC and there is no
part of the PL310 h/w used by the driver.

If there is lots duplication, then that's a sign the framework needs
to handle more of the boilerplate pieces. There could be a "simple"
driver/library for devices which are no more than some registers, an
interrupt handler and static information about the type of EDAC
device.

Rob
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